Radar equipment used on boats commonly includes a scanning unit located at a high point on the boat for sending out and receiving radar pulses, and a display unit located within the boat, on which the operator is presented with a display of the radar field of view, and which incorporates various controls by means of which the operator can modify operations occurring in the scanning unit. These controls will typically generate control signals to control in the scanner unit functions such as the timing of the transmission of radar pulses, the length of the pulses, and the tuning of the radar pulse receiver located in the scanning unit. Also, the gain of the receive may be controlled, and a sea clutter signal may be sent to the scanning unit, this being a signal whose function will be described in detail below.
Further, information signals need to be transmitted from the scanner unit to the display unit, including for example a video signal derived from the received radar echo, and signals indicative of the angular position of the radar scanner, which is rotatable.
It has been usual to transmit these signals by means of a multi-cored conductor extending from the display unit to the vicinity of the scanning unit, at which point multiple slip rings have been employed to transfer the signals from the stationary conductors to the appropriate circuits within the rotatable scanning unit.
In radar for small boats, it is important that the cost be kept as low as possible so as to widen the availability of the equipment to users. It is also important that the equipment be reliable. The multi-cored conductors have needed in the past to have as many as twelve individual conductors and a corresponding number of slip rings have been employed. The conductors are relatively expensive and the chance of a fault occurring due to poor contact is proportionate to the number of slip rings employed.